Comparative Anatomy of the Tunicate Tadpole,ciona Intestinalis

At 19-20 h of age, the Ciona intestinalis ascidian tadpole has six developed organ systems (tunic, epidermis, notochord, tail musculature, adhesive organ, and nervous system) and approximately four organ system rudiments (including: primordial pharynx, atrial primordia, gut primordium, and mesodermal pockets). Contemporary light and electron microscopic descriptions of the anatomy and the histology of these tissues support the old contention, originated by Kowalevsky in 1866, that the body plans of tunicate tadpole and of vertebrate larvae are homologues.